1. Field of the Invention
The present invention generally relates to an end effector for transporting a workpiece such a semiconductor wafer between a transferring chamber and a processing chamber for processing a workpiece, for example.
2. Description of the Related Art
A process of semiconductor manufacturing includes a step of transporting a semiconductor wafer from a wafer-storing cassette to a processing chamber via a transferring chamber using a robotic arm or a step of transporting a semiconductor wafer from a processing chamber to another processing chamber using a robotic arm. The robotic arm is provided with an end effector for loading a wafer thereon and carrying the wafer from one chamber to another. Typically, the end effector does not have a mechanical clamping mechanism for clamping a wafer, and by a wafer positioning or alignment mechanism (e.g., those disclosed in U.S. Patent Application Publication No. 2012/0325148, U.S. Pat. No. 7,963,736, and U.S. Pat. No. 8,041,450, each disclosure of which is herein incorporated by reference in its entirety), a wafer is placed on the end effector for transfer. The wafer stays on the end effector while being carried by friction against a surface of the end effector, which is caused by gravity. As the throughput is increased, the transferring speed by the robotic arm is also increased. When the transferring speed is increased, since the wafer stays on the end effector by friction, the wafer sometimes moves relative to the end effector and slips out of place, thereby causing a transfer error and decreasing transfer stability. At least one embodiment of the present invention can effectively resolve the above problem.
Any discussion of problems and solutions involved in the related art has been included in this disclosure solely for the purposes of providing a context for the present invention, and should not be taken as an admission that any or all of the discussion were known at the time the invention was made.